Many communication systems operate using a centralised scheduler which is responsible for allocating transmission resources to different nodes. A typical example is the uplink of the UMTS LTE (Long Term Evolution), where the uplink transmissions from different secondary stations or mobile station or User Equipments (UEs) are scheduled in time and frequency by the primary station or base station or Node B (eNB). The primary station transmits a “scheduling grant” message to a secondary station, indicating a particular time-frequency resource for the secondary station's transmission typically around 3 ms after the transmission of the grant message. The grant message also typically specifies the data rate and/or power to be used for the secondary station's transmission.
In order for the primary station to issue appropriate grants, it needs to have sufficient information about the amount, type of data and the urgency of it awaiting transmission in the buffer of each secondary station. This information can be used to inform the scheduler in the primary station of either the satisfaction level of individual secondary stations or secondary stations whose service might be close to being dropped.
In LTE, a number of different types of buffer status report (BSR) messages are therefore defined, which may be transmitted from a secondary station to the primary station when certain triggers occur. The state of the art in this respect is defined by the current version of 3GPP TS36.321 (as of June 2008), §5.4.5, incorporated herein by reference.
The Buffer Status reporting procedure is used to provide the serving primary station with information about the amount of data in the Uplink buffers of the secondary station. This is currently defined in 36.321 (as of June 2008), §6.1.3.1 incorporated herein by reference. A problem with this procedure defined in 36.321 is that the content of the buffer status report only identifies the total amount of data in bytes. This gives some information to scheduler but this may not be sufficient for the scheduler in the primary station to make the best possible decision, especially in some situations, as for example when VoIP traffic is being transmitted perhaps together with other services from the secondary station with different Quality of Service (QoS) requirements, where absolute data buffer size in bytes is not the most appropriate measure of how the QoS requirement is currently being satisfied.